The present invention relates to a cooling system for an IC package used in electronic equipment such as an information processor.
Many conventional cooling systems for an IC package employ a cooling scheme wherein a plurality of printed boards each mounting ICs thereon are accommodated in shelves and are cooled by forced convection of air by cooling fans. A forced air cooling scheme of this type is required to deliver a large quantity of air to electronic equipment since recent electronic equipment has a higher heat generation density due to use of LSIs (Large Scale ICs). When the capacity of the forced air cooling system is increased, a high-power cooling fan used therein poses a noise problem. Therefore, the cooling capacity of the cooling system of this type has almost reached maximum capacity.
In another cooling system, a liquid coolant such as water having a heat capacity larger than that of air is circulated near ICs, and metal parts are located in contact with cases of the ICs to conduct heat from the ICs to the coolant, thereby dissipating heat. A typical example of such a cooling system is disclosed in Special Report "SUPERCOMPUTERS DEMAND INNOVATION IN PACKAGING AND COOLING", ELECTRONICS/Sept. 22, 1982, PP. 142-143. In this literature, a plurality of LSIs are brought into contact with a cold plate having a water channel in which a coolant flows, thereby cooling the LSIs.
Heights of LSIs are not necessarily identical due to variations in dimensional precision of parts, mounting variations, warping of a printed board, and the like and cannot be aligned on an identical plane. For this reason, a thermal paste sealed in a film is mounted on a surface of a cold plate which is in contact with an LSI, and variations in LSI heights are absorbed by flexibility of the thermal paste. However, when variations in heights of LSIs exceed a predetermined range and cannot be absorbed by a material such as a thermal paste, air which has a poor heat conduction property is present in a heat conduction path between the LSI and the cold plate, thus degrading the cooling effect.